To realize an inspection apparatus capable of inspecting variation in thickness in a short time for all surfaces of a semiconductor substrate in which a device is formed.

The inspection apparatus includes illumination means (1, 2, and 3) which radiate illumination light that is semi-transparent against a semiconductor substrate, toward a rear surface (7a) on the side opposite to a device formation surface of a semiconductor substrate (7), imaging means (15) which receives the illumination light that has entered the rear surface of the semiconductor substrate, and then reflected on a device structure surface (7b), to come out of the rear surface side, and a signal processing device (20) which detects thickness variation by using an output signal from the imaging means. The signal processing device includes means which uses the output signal from the imaging means to form a two-dimension image (21), photographed from the rear surface side of the semiconductor substrate, of a device formed at the semiconductor substrate, and thickness variation detecting means (22, 23, and 24) for comparing the photographed two-dimension image of the device with a reference image and detecting thickness variation of the semiconductor substrate based on the result of image comparison.